Directly compute degp3

Use definition of EGP3 to directly compute degp3 from dgpd and pgpd.
This simplifies degp3 somewhat.
Compute qegp3 correctly in all cases

This uses C code to accurately compute log(1 - exp(x)).
Fix pegp3 transformations
Simplify logic in regp3

regp3 was essentially a straight copy of qegp3; here we make that
explicit.
Remove unnecessary namespace hackery
Merge pull request #6 from pdmetcalfe/egp3

various {d,p,q} egp3 - related bits of code